This sept had their royal seat at Maistiu (Mullaghmast) in the south of modern County Kildare.
The king lists in the Book of Leinster have Lorcán succeed Ruarc mac Brain (died 862) of the Uí Dúnchada sept and followed by Túathal mac Máele-Brigte (died 854).
[2] Francis John Byrne suggests that the root of this apparent confusion lay in the fact that the Uí Dúnlainge kings exercised little real authority due to the aggressions of their western neighbour Cerball mac Dúnlainge (died 888), King of Osraige.
[3] In 848 Lorcán led the Laigin in alliance with Ólchobar mac Cináeda (died 851) in a victory over the Vikings in the Battle of Sciath Nechtain near modern Castledermot, County Kildare, in which fell the jarl Tomrair.
[4] Lorcán's father Cellach had also been aligned with Munster during the reign of Feidlimid mac Cremthanin (died 847).